Heat-sensing cable



June 21, 1966 J. s. DAvlEs 3,257,530

HEAT-SENSING CABLE Filed Nov. l. 196 2 Sheets-Sheet 1 45 50 INVENTOR.

J/v 5.' a/f/ 'ef June 2l, 1966 J. s. DAvlEs HEAT-SENSING CABLE Filed Nov.

2 Sheets-Sheet 2 INVENTR. J/f 5. m//ef United States Patent O 3,257,530 HEAT-SENSING CABLE John S. Davies, 1010 Norumbega Ave., Monrovia, Callf. Filed Nov. 1, 1963, Ser. No. 320,646 7 Claims. (Cl. ZOO- 143) The .present invention relates to an improved electrical control system for actuating sprinklers, or other tire extinguishing means, in the event of a fire; or for initiating an appropriate alarm, or for performing additional functions, as desired.

The invention is particularly suited for the protection of homes in wooded areas. However, it will become evident as the description proceeds, that the invention has general utility as an economical tire protective means, for homes, crops, acreage, warehouses, and other structures.

It is, accordingly, an object of the present invention to provide .a safe, economical, electrical system which is capable of responding to the presence of tire, or excessive heat, to sound an alarm, actuate water sprinklers or other lire extinguishing means, or to perform other appropriate functions.

Another object of the invention is to provide such an improved electrical control system which, under normal conditions, is in Ia passive state and draws no electrical current; thus permitting the system to be set in readiness at all times, including even extended intervals when the premises are unattended, or when the residents are asleep.

Yet another object of the invention is to provide such an improved system which is relatively easy to install on a do it yourself basis.

In the practice of the invention, in the embodiment to be described, a pair of mutually insulated wires are supported under tension between two support posts. The insulated wires form an elongated strip-like heat-sensing element. yThis element is twisted about its longitudinal axis, as will be explained, and supported under tension, as stated above. Then, should the presence of fire, or excessive heat, cause the insulation in the element to melt, the two wires `are caused to twist around one another into intimate mutual electrical contact.

The above-mentioned twisting of the wires into mutual electrical contact causes an electrical circuit to be completed; and this circuit can be utilized, as will be described, to initiate an alarm and/or to energize a sprinkler system, or to actuate other types of re extinguishing means.

As mentioned above, a feature of thefinvention is the fact that the assembly is extremely inexpensive. The completed assembly requires a minimum of readily available and inexpensive components. Moreover, as will be described, the assembly Ymay be'installed in a simpleand inexpensive manner.

Another feature of the invention is that it is intrinsically safe, since it can operate on low voltage levels and since all its electrical components are normally insulated and unexposed. Furthermore, as mentioned above, under normal stand-by conditions, the system does not draw current, although this does not in any way militare against the system being fully conditioned to respond immediately to the presence of fire, or the like.

Although the invention has particular utility in the protection of homes from brush rires, and the like, especially during the absence ofthe residents, the system of the invention'can also be used for the protection of warehouses, and other structures. -Moreover, the system finds particular use in the protection of missile sites, and other military installations, from lire hazard.

As will be described, the sensing capabilities of the system can be made selective, so that the system can be used to indicate at a central control point the presence of lire, or other unusual temperature conditions, at different vmonitored areas. These areas may, .for example, be different iioors or sections of a warehouse or other structure; diferent crop iields, or lots, or acreages in a range of protected areas, and so on.

As mentioned above, the present invention provides an improved electrically controlled fire extinguishing and/or alarm system. The system includes, as noted, a sensing means in the form of a tensioned, twisted, insulated element, the element being composed of a pair of Iwires and a strip of flexible insulating material. The insulating material may, for example, be a selected resin, plastic or the like, which will melt when heated or exposed to flame. Such melting of the insulating material results in the wires spinning together and electrically contacting one another. This mutual electrical contacting of the wires causes an electric circuit to be established .to a sprinkler control system, or to other fire extinguishing means. In addition, or alternately, the electric circuit may be completed to an alarm or other instrumentality.

As Ialso mentioned, the system of the invention can be made selective to different areas, or locations, and signals corresponding to the respective areas can be transmitted to a central control point. The control point can be remote from the actual structure, or area, for example, and telephone lines or other communication means may be used to transmit the signals to the remote central point.

The actual insulating lmaterial forming the strip ofthe temperature sensitive element can be selected to melt in the presence of flame, or at selected temperatures. Well known resins are avail-able for this purpose. In Ithis manner, diiierent heat sensitive units can be constructed -and provided in the combination of the invention for diiferent purposes. It has been found that the well-known television antenna lead-in wire is ideally suited Ifor usual rire protection purposes. This lead-in wire comprises a flat flexible strip of insulating material, and it has a pair of wires supported in spaced and parallel relationship at the opposite edges of the strip. When such a stripV is twisted and mounted under tension between the aforementioned support posts, it is ideally suited as .the sensing element for the system. It has been found that in the presence of flame, the insulation strip separating the wires melts, and that the wires spin together into a mutually electrical contacting relationship.

The aforementioned sensing element may be originally provided in its usual untwisted form, and it may be twisted about its longitudinal axis during the installation of the system. However the installation of the system may `be further simplified by providing the sensing element with the insulation strip in a pre-twisted configuration. Then, it is merely necessary for the pre-twisted sensing element to be cut to desired lengths, and for the separate lengths to be mounted under tension between the pairs of support posts, in a manner to be described.

The system of the invention, as noted, normally does not draw electric current so that it is particularly suited to battery operation. Batteries can be used in areas where power is not available, or on stand-by :basis in case of power failure. In the latter instance, a usual battery charging means can be provided to assure that the battery is maintained in a fully charged condition at all times.

Other features and advantages of the system of the invention will become apparent froma consideration of the following specication, when the specification is considered in conjunction with the accompanying drawings, in which:

FIGURE l illustrates the fire prevention/extinguishing system of the present invention installed around a home, and connected to actuate a sprinkler system automatically in the presence of a brush fire reaching the outer limits of the lot on which the home is situated;

FIGURE 2 is a representation of one embodiment of the invention, and of associated circuitry and electrically controlled components, the illustrated embodiment ysurround the premises.

being utilized, for example, tov control a water sprinkler system;

FIGURE 2A is a perspective view of a clamp used in the vembodiment of FIGURE 2;

FIGURE 3 is a representation of a second embodiment of the invention, in which the re prevention system of the invention is used for the selective monitoring of different areas;

FIGURE 4 is a fragmentary representation of one form of sensing element which may be used in the system of the invention;

FIGURE 5 is a cross-sectional view of the sensing element of FIGURE 4, taken substantially on the line v5---5 of FIGURE 4;

FIGURE 6 shows the manner in which the sensing element of FIGURE 5 is held in a normally tensioned, twisted condition; and the manner in which the conductors of the sensing element are caused to twist together into mutual electrical contact, upon the insulating material in the heat-sensing element becoming melted; and

FIGURE 7 is a fragmentary perspective View of the manner in which the ends of adjacent sensing elements a-re normally mounted on a support post, in accordance' with one embodiment of the invention.

As mentioned above, a major use for the improved fire prevention/extinguishing, and/or alarm system of the present invention is in the protection of homes, and especially for protecting homes and landscaping situated in wooded areas, or in areas containing a large quantity of brush.

For such an installation, the sensing system of the invention includes a plurality of supp-ort .posts 10. These posts are mounted on any appropriate pedestals, such as blocks of concrete or wood 12 (FIGURE 2), so that they may be rigidly supported at spaced intervals around the property. In many cases, for example, the sensing system is supported on the fence posts of the usual fence surrounding the property.

The posts are spaced apart by predetermined distances, and, as shown in FIGURE 1, they completely The height of each of the posts 10 is dictated lby the height of grass, brush, or other inflammable substance which would become ignited upon the approa-ch of a brush fire, or the like. As noted, the posts 10 in same instances would be the fence posts of the fence surrounding the property.

The heat-sensing elements of the invention are designated 14, and these elements are suspended between corresponding ones of the posts 10.

A connection is made from the sensing elements to a v control box 16 adjacent the house. A water sprinkler system 18 is provided for watering the area surrounding the house. This system may include sprinkler outlets on the roof of the house, if so desired. The sprinkler system is under the cont-rol of the control box I16, as will be described.

A connection may also -be made the electric energy circuit of an electric pump located in a water tank, or swimming pool. This pump serves to supply water to the sprinkler system in the event that the water pressure in the water mains failed.

Now, should a fire approach the boundaries of the protected lot, one or more of the sensing elements 14 responds to the heat and flames of the re, in a manner to be described, so as to complete an electric connection. This electric connection causes electrical controls in the control Ibox 16 to become energized,.and these controls automatically turn on the the sprinkler system 18. The sprinkler system then causes the entire area to be watered, so as to prevent the fire from reaching the dwelling place, or destroying the landscaping. y

The support posts 10 may be in the form of carriage bolts, which are shown in FIGURE 2, or they may have any other suitable conguration. As mentioned, the support posts are rigidly supported in the blocks 12, or on the fence surrounding the property.

,the secondary of the transformer 42.

The sensing element 14 itself is in the form shown for Y example in FIGURES 4 and 5. That is, the sensing element 14 includes an elongated strip 22 of flexible plastic insulating material, and 'a pair of lexible multi-strand electrical wire conductors 24 and 26 at opposite edges of the insulating strip. As mentioned above, the strip may be yformed of t-he usual television antenna lead-in Wire.

One end of the strip 22 is looped through a clip-26, and clamped by a clamp 28. -The clip 26 is supported in apertures in the head 10a of the corresponding support post 10. The clamp 28 may be of the usual manually adjustable screw type, as shown in FIGURE 2A.

The other end of the sensing element 14 is looped through the clip 17, and clamped by a clamp 30. The clamp 30 may be similar to the clamp 28.

As shown in FIGURE 2, for example, the sensing element 14 is supported between the support posts 10 in a twisted configuration, and under tension by the spring 16. The clip 26 has a bifurcated configuration, and it extends through two holes in the corresponding top 10a, to prevent the sensing element 14 from turning and hold it in its twisted configuration.

It will be appreciated that under normal conditions, the fwire conductors 24 and 26 in the sensing element 14 are held in a spaced, mutually insulated relationship. Howeve-r, the insulating material forming the strip 22 is cornposed of a selected plastic material, which Lwill melt in the presence of lire, or excessive heat. Such melting of the insulatingmaterial causes the wire conductors 24 and 26 to spin together into a close mutual electrical contact, as shown in FIGURE 6.

In the embodiment of FIGURE 1, all of the wire conductors 24 in the various sensing elements 14 are connected together, as are all of the wires 26. The Wires are connected to the control box 16 through a pair of leads 40. A transformer 42 may be provided at the control box 16 (FIGURE 2) to reduce the norm-al alternating current line voltage to a safe level of, for example, from 10-12 volts.

The leads 40 are connected in series, for example, with an alarm element 44 across the secondary winding of the transformer 42. A solenoid control element 46 of a solenoid valve 48 may be connected in shunt across the alarm'44. The solenoid valve 48 is connected into t-he ysupply Water pipe 50 of the sprinkler system 18. If so desired, a manually controlled valve may be connected in parallel with the valve 48, for normal operation of the sprinkler system.

It follows, t-herefore, that whenever the insulation strip 22 of a sensing element 14 melts, the resulting contact of the wire conductors 24 and 26 closes the circuit across This immediately energizes the alarm 44, and it also activities the solenoid element 46. The resulting activation of the solenoid element 46 turns on the sprinkler system 18, so as to water the ent-ire area.

The solenoid element 46 may include a usual holding contact, so that the valve 48 continues to be energized, even though the particular sensing element may subsequently be consumed by're to open circuit the connec- 4tion to the secondary of the transformer 42.

vides a simple and inexpensive means for protecting the premises from brush -res and the like.

As mentioned above, however, the invention has wider utility, in that the sensing elements 1'4 may be mounted at any place inside or outside a structure, where there may be a likelihood of ltire. Als-o, by a suitable selection of the materi-al of the insulating strip 14, the system of the invention can be used to respond to excessive temperatures, for example, and not necessarily to actual fire.

The embodiment of FIGURE 3 is generally similar to the embodiment described above, and like elements have been identified by the same num-bers.

In the embodiment of FIGU'RE 3 the leads 60 form a common connection to one of the wires in the successive 'sensing elements 114. However, the leads 62 constitute separate leads from the other wire of each of the sensing elements 14.

The system of FIGURE 3 includes a plurality of alarm units. 64 which are connected to respective ones of the leads 62. This seconda-ry of the transformer 42 is connected to the leads 60 and to a common llead 66, the latter common lead being connected to the alarm unit 64.

It follows, therefore, that should any one of the sensing elements 1'4 respond to a re, or excessive temperature condition, a circuit 4is established between the common connection provided by'the leads 60, and its particular separate lead 62. Therefore, a corresponding one of the alarms 64 is actuated.

The system of FIGURE 3 enables an operator at a central station to determine which particular sensing unit h-as been actuated, so that the locality of the tire, or other hazardous condition, is made known to him. This permits the operator to take any necessary action. Of course, the separate alarms 64 may be replaced by automatically actuated lire-extinguishing or fire-prevention units, if desired; such units being placed atthe particular areas monitored by the different sensing elements.

The invention provides, therefore, an improved and inexpensive lire extinguishing, preventing and/or alarm system. The system is intrinsically safe in that it operates at low voltage levels. Also, no electrical conductors are normally exposed, and no electrical current flows during the stand-by condition of the system.

As described, the system of the invention incorporates unique electrical sensing elements which establish an electrical connection in the presence of the monitored hazardous condition. lThis electrical connection may be used, as described, t-o activate a water sprinkler system, or any other appropriate type of ire extinguishing or prevention system.

In addition, or as an alternative, the control system of the invention may be used to sound an alarm.

As also described, the control system can be constructed on a selective'basis, so that different areas can be individually monitored.

While particular embodiments of the invention have been shown and described, modifications may be made. It is intended in the claims to cover all modifications which fall within the concept of the invention.

What is claimed is:

l1. An electrical control system including: an elongated heat-sensing element comprising a plurality of twisted electric Wires and `temperaturesensitive insulating material normally holding said wires insulated from one another, supporting means including iirst and second spaced support members, and means for mounting saidelongated heat-sensing element minder tension between said first and second support members so .as to cause said electric Wires to electrically contact one another upon the reaction of said insulating material to temperatures above a particular threshold.

y2. An electrical control system including: an elongated heat-sensing element comprising a plurality of twisted electric wires and an insulating material normally holding said wires in a mutually spaced and insulated reand a strip of insulating material normally holding said wires in mutually spaced and insulated relationship, said insulating material having a melting point at a particular temperature threshold, supporting means including lirst and second spaced support members, and resilient means mounting said elongated heat-sensing element in a twisted coniiguration under tension between said first and second support members so as to cause said electric wires to twist together and electrically contact one another upon the melting of said insulating material in response to temperature above said particular threshold.

4. An electric control system including: an elongated heat-sensing element comprising a pair of twisted electric wires and a iiat web of temperature-sensitive material normally holding said twisted wires separated and spaced from one another a distance greater than the diameter of the individual wires; and means mounting said elongated heat-sensing element under tension to cause said electric wires to contact one another electrically upon the reaction of said temperature-sensitive material to temperatures above a particular threshold.

5. An electrical control system including: an elongated heat-sensing element comprising a pair of twisted electric wires, and a strip of insulating material normally holding said Wires separated and spaced from one another a distance greater than the diameter of the individual wires, said insulating material softening when a particular temperature threshold lis reached; and resilient means mounting said elongate-d heat-sensing element in a twisted configuration under tension` so as to cause said electric wires to Itear out of' said strip of insulating material and twist together into electrical contact as said threshold ds reached.

6. An electrical control system including: an elongated heat-sensing element comprising a pair of twisted electric wires, and a strip of insulating material normally holding said w-ires separated and spaced from one another a distance greater than the diameter of the individual Wires, said insulating material having a melting point at a particular temperature threshold and softening as that threshold is approached; and resilient mea-ns mounting said elongated heat-sensing element in a twisted conguration under tension so .as to cause said electric wi-res to tear out of said strip of insulating material and twist together into electrical contact as said threshold is approached.

7. The control system deiined in claim 6 in which said strip of insulating material is in the form of a flat web, Iand said wires are respectively supported along the outer edges of said web.

References Cited by the Examiner UNITED STATES PATENTS 1,140,837 5 /119115 Ma-rcante. 2,185,944 1/1940 Holmes. 2,196,592 4/1940 Lowe et al. 3,014,206 12/ 1961 Slavin 340--227 X FOREIGN PATENTS v 13,001 7/1890 Great Britain. of 1889 NEIL C. READ, Primary Examiner.

R. M. ANGUS, Assistant Examiner. 

4. AN ELECTRICAL CONTROL SYSTEM INCLUDING: AN ELONGATED HEAT-SENSING ELEMENT COMPRISING A PAIR OF TWISTED ELECTIC WIRES AND A FLAT WEB OF TEMPERATURE-SENSITIVE MATERIAL NORMALLY HOLDING SAID TWISTED WIRES SEPARATED AND SPACED FROM ONE ANOTHER A DISTANCE GREATER THAN THE DIAMETER OF THE INDIVIDUAL WIRES; AND MEANS MOUNTING SAID ELONGATED HEAT-SENSING ELEMENT UNDER TENSION TO CAUSE SAID ELECTRIC WIRES TO CONTACT ONE ANOTHER ELECTRICALLY UPON THE REACTION OF SAID TEMPERATURE-SENSITIVE MATERIAL TO TEMPERATURES ABOVE A PARTICULAR THRESHOLD. 